I've never touched on this in education or anything, but I'll try and help.
Country boarders and the boundaries between are vital because of the exact reasons you've stated - politics, region and culture. It also has to do with economics, demographics and similar topics.
Politics- Different laws for different countries. If the same laws were imposed on every country, it would not work. The Middle East have very Islamic based, very strict laws. These would not work here in the UK, like ours wouldn't over there. There is also political tension between many countries, so having them bound wouldn't be a smooth turnout. The only way to free up boundaries would be to have no boarders - this can also have an effect on economics.
Economics - globalisation. How can you strengthen a country if all resources are shared equally across the globe. There is not enough - if there were no boarders, the whole world, continent, whatever has one government. If say, the EU became one country, and money was put together, there would be literally a standstill in the growth of the UK as money is used to fund poorer places such as Albania and Poland. If its all treated as one country, surely money should be funded to the poor right?
Culture, demographics and religion - exactly whats going on with the Middle East. Different cultures, races etc fighting over differences and land.
Darwins theory could have a connection, as we have all evolved from the first humans, originating from Africa. We have evolved differently, obviously as we see different features across the world, from European decent, African, Asian, Hispanic..
If there is a connection, then its due to the differentiation in humans, leadings to different cultures and seperation of beliefs and religions etc.